Deinking of Flexographic Newsprint, 2008 Engineering, Pulping and Environmental Conference

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A semi-continuous flotation cell, which incorporates an electrolytic cell, was used to collect inks from newsprint pulp slurry. In one case, 100% flexographic newsprint was treated. The effect of pulping time, temperature, and an electric field on deinking efficiency was investigated. Increasing the pulping time from 5 to 20 minutes drastically reduced the percent reduction in effective residual ink concentration (ERIC) by 5% percent. The deinking efficiency is improved by 3% and 5% when the temperature from 25^oC to 43^oC and when an electric field is used respectively. In another case, 48% flexographic newsprint was treated. The effect of float consistency, sodium hydroxide dosage, surfactant concentration, and electric field on deinking efficiency was investigated. An electric field treatment improved deinking efficiency, as much as 7% compared to when electric field is not used. Thermogravimetric analysis was used to corroborate ERIC measurement. Deinking selectivity was discussed using a Z-weighted factor parameter.